1. Field of the Disclosure
This disclosure relates generally to systems, methods and devices for obtaining drilling assemblies that utilize an orientation sensing system.
2. Description of the Related Art
Valuable hydrocarbon deposits, such as those containing oil and gas, are often found in subterranean formations located thousands of feet below the surface of the Earth. To recover these hydrocarbon deposits, boreholes or wellbores are drilled by rotating a drill bit attached to a drilling assembly (also referred to herein as a “bottomhole assembly” or “BHA”). Such a drilling assembly is attached to the downhole end of a tubing or drill string made up of jointed rigid pipe or a flexible tubing coiled on a reel (“coiled tubing”). For directional drilling, the drilling assembly may use a steering unit to direct the drill bit along a desired wellbore trajectory.
Wellbore drilling systems may also use measurement-while-drilling (MWD) and logging-while-drilling (LWD) devices to determine wellbore parameters and operating conditions during drilling of a well. These parameters and conditions may include formation density, gamma radiation, resistivity, acoustic properties, porosity, and so forth. Many of these tools are directionally sensitive in that, to be meaningful, the measurements made by these tools should be correlated or indexed with a frame of reference for the formation. In one convention, the angular difference between a reference vector on a tool and a vector of reference is referred to as a toolface angle. The reference vector may be borehole highside or magnetic north. As is conventionally understood, the term “borehole highside” is an uppermost side of a non-vertical borehole. It is commonly desired to present the output from imaging sensors oriented with reference to the borehole highside.
The measurement of borehole highside may be made using devices such as a three-axis accelerometer positioned on the directionally-sensitive tool. Often, a drill string may include two or more directionally sensitive tools. While each such tool may include an orientation sensor, such an arrangement may be expensive and complex. A single sensor may be used for a plurality of directionally-sensitive tools if the angular alignment of these tools is known. Because wellbore tools are often assembled using threaded connections, a plurality of directionally-sensitive tools may not be rotationally aligned within acceptable tolerances. That is, for example, due to machining variations, two directionally-sensitive tools that are configured to point in the same direction could have an angular offset. Thus, conventionally, the angular or rotational offset between directionally sensitive tools are manually measured and recorded after these tools have been assembled. Manual measurement of rotational offsets or mismatches between two or more directionally-sensitive tools may be susceptible to errors and may be difficult in certain drilling conditions. For example, for offshore applications, rough seas may make manual measurement of rotational offsets difficult.
The present disclosure is directed to addressing one or more of the above stated drawbacks for determining the orientation of logging tools and other elements of a drilling system.